中国物理B ›› 2017, Vol. 26 ›› Issue (8): 86301-086301.doi: 10.1088/1674-1056/26/8/086301

• CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES • 上一篇    下一篇

Elastic, vibrational, and thermodynamic properties of Sr10(PO4)6F2 and Ca10(PO4)6F2 from first principles

Xianggang Kong(孔祥刚), Zhihong Yuan(袁志红), You Yu(虞游), Tao Gao(高涛), Shenggui Ma(马生贵)   

  1. 1 Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China;
    2 College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, China;
    3 Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064, China
  • 收稿日期:2017-04-13 修回日期:2017-05-15 出版日期:2017-08-05 发布日期:2017-08-05
  • 通讯作者: Tao Gao E-mail:gaotao@scu.edu.cn
  • 基金资助:

    Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA034202) and the National Natural Science Foundation of China (Grant No. 11305147).

Elastic, vibrational, and thermodynamic properties of Sr10(PO4)6F2 and Ca10(PO4)6F2 from first principles

Xianggang Kong(孔祥刚)1, Zhihong Yuan(袁志红)1, You Yu(虞游)2, Tao Gao(高涛)1,3, Shenggui Ma(马生贵)1   

  1. 1 Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China;
    2 College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, China;
    3 Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064, China
  • Received:2017-04-13 Revised:2017-05-15 Online:2017-08-05 Published:2017-08-05
  • Contact: Tao Gao E-mail:gaotao@scu.edu.cn
  • About author:0.1088/1674-1056/26/8/
  • Supported by:

    Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA034202) and the National Natural Science Foundation of China (Grant No. 11305147).

摘要:

The electronic, elastic, vibrational, and thermodynamic properties of Sr10(PO4)6F2(Sr-FAP) and Ca10(PO4)6F2(Ca-FAP) are systematically investigated by the first-principles calculations. The calculated electronic band structure indicates that the Sr-FAP and Ca-FAP are insulator materials with the indirect band gap of 5.273 eV and 5.592 eV, respectively. The elastic constants are obtained by the “stress-strain” method, and elastic modulus are further evaluated and discussed. The vibrational properties, including the phonon dispersion curves, the phonon density of states, the Born effective charge, and associated longitudinal optical and transverse optical (LO-TO) splitting of optical modes, as well as the phonon frequencies at zone-center are obtained within the linear-response approach. Substitution of Ca by Sr causes phonon frequencies to shift to lower values as expected due to the mass effect. Additionally, some phonon-related thermodynamic properties, such as Helmholtz free energy F, internal energy E, entropy S, and specific heat CV of Sr-FAP and Ca-FAP are predicted with the harmonic approximation. The present calculated results of two apatites are consistent with the reported experimental and theoretical results.

关键词: Sr-FAP, Ca-FAP, TDOS, elastic modulus, thermodynamic properties

Abstract:

The electronic, elastic, vibrational, and thermodynamic properties of Sr10(PO4)6F2(Sr-FAP) and Ca10(PO4)6F2(Ca-FAP) are systematically investigated by the first-principles calculations. The calculated electronic band structure indicates that the Sr-FAP and Ca-FAP are insulator materials with the indirect band gap of 5.273 eV and 5.592 eV, respectively. The elastic constants are obtained by the “stress-strain” method, and elastic modulus are further evaluated and discussed. The vibrational properties, including the phonon dispersion curves, the phonon density of states, the Born effective charge, and associated longitudinal optical and transverse optical (LO-TO) splitting of optical modes, as well as the phonon frequencies at zone-center are obtained within the linear-response approach. Substitution of Ca by Sr causes phonon frequencies to shift to lower values as expected due to the mass effect. Additionally, some phonon-related thermodynamic properties, such as Helmholtz free energy F, internal energy E, entropy S, and specific heat CV of Sr-FAP and Ca-FAP are predicted with the harmonic approximation. The present calculated results of two apatites are consistent with the reported experimental and theoretical results.

Key words: Sr-FAP, Ca-FAP, TDOS, elastic modulus, thermodynamic properties

中图分类号:  (First-principles theory)

  • 63.20.dk
65.40.Ba (Heat capacity) 71.20.-b (Electron density of states and band structure of crystalline solids) 65.40.gd (Entropy)